JPH0845516A - Plate type solid electrolyte fuel cell using mesh with different wire diameters - Google Patents

Abstract

PURPOSE:To improve the current collecting efficiency and the absorption rate of internal stress of a fuel cell, so as to improve the performance, by making the wire diameter of a heat-resisting metallic mesh, the finer at the layer the closer to a fuel electrode. CONSTITUTION:A mesh 7 is divided into several sections on the plane by dividers 10, and it has the area to cover all the surface of the fuel electrode of a unit cell. The wire diameter of the mesh 7 is made finer at the layer near the fuel electrode of the unit cell, and composed of a rough meshwork with the larger wire diameter at the other layers. When the wire diameter of the mesh is fine, the meshwork is made smaller, and the mesh contacts closely to the electrode so as to increase the conductivity and improve the current collecting efficiency. And since the wire diameter is large at the mesh near a separator, the meshwork is made larger so as to facilitate the ecconomy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate type solid electrolyte fuel cell using a mesh or felt of nickel or other heat resistant metal having different wire diameters between a fuel electrode and a separator.

[0002]

2. Description of the Related Art Recently, for example, oxygen and hydrogen, respectively,
As an oxidant and a fuel, an electrolyte fuel cell, which directly converts chemical energy originally possessed by the fuel into electric energy, has been attracting attention from the viewpoints of resource saving and environmental protection. In particular, flat plate solid oxide fuel cells have high operating temperature, high power generation efficiency, and high overall efficiency due to the use of high-temperature waste heat.

In this flat plate type solid electrolyte fuel cell, a flat plate type cell in which a fuel electrode and an air electrode are arranged so as to sandwich a flat plate type solid electrolyte layer and an adjacent single cell are electrically connected in series and This is configured as a multi-layer stack by alternately stacking separators for distributing fuel gas and oxidant gas on a single cell. Usually, the solid electrolyte layer is made of a zirconia sintered body (YSZ) doped with yttria or the like,
Ni / YSZ cermet as a fuel electrode and (La, Sr) MnO ₃ as an air electrode were coated on both surfaces by screen printing or the like.

The internal manifold type solid oxide fuel cell has an integral structure in which the separator has the functions of supplying and discharging, distributing, and electrically connecting an oxidant and a fuel gas. Therefore, a gas supply / exhaust hole is formed in the side portion of the separator, the gas is supplied / exhausted from the hole to the electrode surface of the unit cell, and further, in order to evenly distribute the gas in every corner of the electrode surface, and A large number of grooves are formed on the electrode surface to connect adjacent cells in series. On the other hand, gas supply / exhaust holes are formed in the portion of the solid electrolyte layer of the unit cell where no electrode is attached, and these holes are connected in the process of stacking the unit cells to form a gas passage inside the stack. A spacer is hermetically sandwiched between a portion of the surface of the separator facing the fuel electrode side of the unit cell, which is not in contact with the electrode, and a surface of the solid electrolyte layer of the unit cell, which does not have an electrode.

Further, the flat plate-shaped heat-resistant metal mesh or felt becomes a single layer or multiple layers, and is sandwiched between the fuel electrode of the unit cell and the surface of the separator facing it in an elastically compressed state. There is. This is used for improving the efficiency of current collection and distribution of fuel gas. The heat resistant metal is, for example, Ni, Ni—Cr alloy, or Fe—Cr alloy. The use of this mesh improves the current collection efficiency of the solid oxide fuel cell, but due to the thermal cycle that the electrolyte fuel cell receives at an operating temperature of 1000 ° C., the metal that is the material of the mesh that contacts the upper surface of the fuel electrode and the fuel Due to the difference in the coefficient of thermal expansion between Ni / YSZ cermet as the material of the electrode and YSZ which is the material of the solid electrolyte layer adhered to the lower surface of the fuel electrode, the solid electrolyte layer, especially its peripheral portion, undergoes thermal stress cracking. Cause and destroy.

[0006]

However, even if a mesh or felt of a heat-resistant metal such as nickel is simply sandwiched between the fuel electrode and the separator, the nickel and the fuel electrode are welded at 1000 ° C. and are cooled. There is a drawback that stress cracking occurs due to thermal cycling due to mismatch of thermal expansion coefficients.

The present invention has been made in view of the above points. By using heat resistant metal meshes having different wire diameters, the current collection rate is improved and stress cracking of the solid electrolyte layer due to thermal cycle is prevented, It is an object of the present invention to provide a flat plate type solid electrolyte fuel cell capable of performing efficient safe operation for a long period of time.

[0008]

In order to solve the above-mentioned problems, the present invention electrically connects a flat-type cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer and an adjacent cell to each other. The cells connected in series and separators that distribute the fuel gas and the oxidant gas to each cell are alternately laminated, and the surface of the cell and the surface of the cell that does not contact the electrode of the separator facing the fuel electrode side of the cell. A spacer is sandwiched in an airtight state between the surface of the solid electrolyte layer where no electrode is present, and a plurality of layers of heat resistance are provided between the surface of the separator facing the fuel electrode side of the unit cell and the fuel electrode of the unit cell. In a flat plate type solid electrolyte fuel cell in which a flexible metal mesh is sandwiched in an elastically compressed state,
The wire diameter of the heat resistant metal mesh is thinned in a layer close to the fuel electrode of the unit cell. Further, the present invention is characterized in that the heat-resistant metal mesh is divided into a plurality of layers in a plane close to the fuel electrode, and the layer in contact with the separator is integrated into one layer.

[0009]

[Function] A plurality of heat-resistant metal meshes (hereinafter referred to as meshes) are interposed between the separator and the fuel electrode, and the mesh diameter of the mesh closer to the fuel electrode is smaller, so the mesh also becomes finer and the fuel electrode The close contact improves the current collection efficiency and also absorbs the internal stress due to the difference in thermal expansion in the battery. Further, the mesh is divided into a plurality of planes in a layer close to the fuel electrode, and the layers in contact with the separator are gathered into one sheet, so that the internal stress is dispersed closer to the fuel electrode and the collection efficiency is improved. To do.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of the flat plate type solid electrolyte fuel cell of the present invention, and FIG. 2 is a perspective view showing a part of the internal structure of the flat plate type solid electrolyte fuel cell of the present invention.

In the flat plate type solid electrolyte fuel cell of the present invention, a flat plate type cell 3 in which a fuel electrode 5 and an air electrode 6 are arranged so as to sandwich a solid electrolyte layer 4 and an adjacent unit cell 3 are electrically connected in series. , And separators 1 for distributing the fuel gas and the oxidant gas to each unit cell are alternately laminated.

The separator 1 is a flat plate-type sintered body obtained by pressure-molding strontium dough tan chromite and firing it in air. Gas supply and exhaust holes are opened in the four corners,
Further, in order to evenly distribute the gas to every corner of the electrode surface of the unit cell 3, the electrode surface is provided with a groove 1c. Groove 1c and groove 1
Between c, the protrusions 1b are provided to connect the adjacent cells 3 in series.
Has become. The front surface groove 1c communicates with two diagonal left and right air supply / exhaust holes, and the back surface groove 1c communicates with two left and right diagonal air supply / exhaust holes. Separator 1
The peripheral portions of the front surface and the back surface of the above are surfaces to be overlapped with the spacer 2 or the solid electrolyte layer 4 of the unit cell 3.

The spacer 2 is made of partially stabilized zirconia or refractory metal and is about 150 microns thick. A substantially square hole is formed in the center, and gas supply / exhaust holes are formed in the four corners on the diagonal. The peripheral portions of the front surface and the back surface of the spacer 2 serve as sealing surfaces for overlapping the separator 1 or the solid electrolyte layer 4 of the unit cell 3.

The unit cell 3 is formed by coating Ni / YSZ cermet as the fuel electrode 5 and (La, Sr) MnO ₃ as the air electrode 6 by screen printing so as to sandwich the solid electrolyte layer 4. The solid electrolyte layer 4 is made of a zirconia sintered body (YSZ) doped with yttria or the like. Gas supply / exhaust holes are formed at four corners of the solid electrolyte layer 4. The gas supply / exhaust holes have the same size and arrangement as those of the separator 1. Further, the peripheral portions of the front surface and the back surface of the solid electrolyte layer 4 are surfaces for overlapping the separator 1 or the spacer 2.

A plurality of layers of mesh 7 or felt are interposed between the separator 1 and the fuel electrode 5 in an elastically compressed state. In FIG. 2, two layers of meshes 7A and 7B are interposed, the mesh 7A contacts the separator 1, and the mesh 7B contacts the fuel electrode 5. Although not shown, the mesh 7A, 7
A mesh 7 having an arbitrary number of layers is interposed between B as required. The mesh 7 is divided into a plurality of pieces in a plane by the dividing portion 10 (the mesh 7B is divided into four pieces in FIG. 2), and has a size that covers the entire surface of the fuel electrode 5 of the unit cell 3. There is. However, the mesh 7A that comes into contact with the separator 1 is not divided but is integrated into one sheet in order to improve current collection efficiency. The wire diameter of the mesh 7 is made thin in a layer close to the fuel electrode of the unit cell, and the other layers are made of a coarse mesh having a large wire diameter.

The mesh 7 is made of a heat resistant metal such as nickel and has good electron conductivity and stretchability in a reducing atmosphere. If the wire diameter of the mesh is small, the mesh of the mesh is naturally small, so that the mesh is in close contact with the electrode, the conductivity is improved, and the current collection efficiency is improved. Also, the separator 1
Since the wire diameter of the mesh close to is large, the mesh becomes large, which is economically advantageous. The diameter of all meshes is thin,
It is economically disadvantageous to use a small mesh.

Each gas is supplied to the flat plate type solid oxide fuel cell having the above-mentioned structure from the gas supply holes in the peripheral portion thereof, flows on the surfaces of both electrodes of the unit cell 3, and is discharged from the gas exhaust holes in the peripheral portion. By doing so, electric power is generated.

[0019]

As described above, according to the present invention, a plurality of layers of nickel or cobalt mesh are elastically compressed between the surface of the separator and the fuel electrode of the unit cell,
By changing the wire diameter of the mesh and thinning the mesh of the layer close to the fuel electrode, the following excellent effects can be obtained. (1) Disperse and absorb the internal stress generated due to the difference in thermal expansion between the mesh and the fuel electrode during the thermal cycle of the fuel cell, and improve the durability of the cell. (2) The efficiency of current collection is improved and the performance of the battery is improved. (3) The mesh of the layer close to the fuel electrode is made thin, and the other layers are made of coarse mesh having a large wire diameter, which is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a flat plate type solid electrolyte fuel cell of the present invention.

FIG. 2 is a perspective view showing a part of the internal structure of the flat plate type solid electrolyte fuel cell of the present invention.

[Explanation of Codes] 1 Separator 2 Spacer 3 Single Cell 4 Solid Electrolyte Layer 5 Fuel Electrode 6 Air Electrode 7 Mesh 10 Dividing Part

Claims (5)

[Claims] 1. A flat plate type cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and adjacent cell units are electrically connected in series, and a fuel gas and an oxidizer are provided in each cell unit. By alternately laminating separators for distributing gas, a plurality of layers of heat resistant metal mesh are elastically compressed between the surface of the separator facing the fuel electrode side of the unit cell and the fuel electrode of the unit cell. In the sandwiched flat plate type solid electrolyte fuel cell, the wire diameter of the heat-resistant metal mesh is thinned in a layer close to the fuel electrode of the unit cell. 2. The heat resistant metal mesh is divided into a plurality of planes in a layer close to the fuel electrode, and the layers in contact with the separator are combined into one sheet. Flat-plate solid oxide fuel cell. 3. The plate type solid electrolyte fuel cell according to claim 1, wherein the heat resistant metal is nickel. 4. The flat-plate solid electrolyte fuel cell according to claim 1, wherein the mesh is felt. 5. A spacer is sandwiched between a surface of the separator facing the fuel electrode side of the unit cell which is not in contact with the electrode and a surface of the solid electrolyte layer of the unit cell where the electrode is not present in an airtight state. The flat plate type solid electrolyte fuel cell according to claim 1, which is characterized in that.